In processing photographic materials containing at least one silver halide-containing layer, development is usually conducted in the presence of hydroquinone, catechol, aminophenol, phenylenediamine, pyrazolidone, reductone or hydroxylamine derivative. Development is usually conducted in an alkaline medium and, in this situation, the developer solution in many cases further contains such additives as sulfites for stabilization, pH-buffering substances and anti-foggants. In order to increase the stability of the developer, it is particularly important from a practical view to add a highly concentrated sulfite. In some cases, development of photographic materials is conducted in the presence of a silver halide solvent for obtaining special effects. For example, it has been known to add a divalent sulfur compound such as a mercapto compound, a thioether or thioamide, a thiocyanate, a highly concentrated sulfite or thiosulfate for the abovedescribed purpose. Developers containing such additives are known as fine grain developers or intermediate grain developers (Grant Haist, Modern Photoqraphic Processing, published by Wiley-Interscience in 1979, pp. 225-229).
Another important embodiment of using the silver halide solvent is a mono-bath develop-fixing solution described in G. Haist, Monobath Manual, published by Morgan Co. in 1960. Developers containing the silver halide solvent or a highly concentrated sulfite usually dissolve a comparatively large amount of silver salt out of silver salt layers of photographic materials. Silver salts dissolved in the developer are then reduced with a developing agent to become fine metallic silver, forming a sludge in the solution. In the case of conducting development using a developer containing a large amount of the silver halide solvent by means of a conveyingtype automatic developing machine, a large amount of silver salt is dissolved, and hence a serious problem of deposition of the sludge arises. This deposition is particularly serious when the processing is conducted at high temperatures. The sludge deposits as massive pieces on various positions of the conveying-type automatic developing machine for use in development processing, such as rollers and belts, staining the surface of films or flaw films, thus deteriorating the finished quality of photographic pictures. Therefore, it is particularly important with photographic light-sensitive materials for printing use to decrease the silver stain of films to the greatest extent possible.
As antisludging agents for such purpose, there have been. known 2-mercapto-1,3,4-thiadiazoles (British Patent No. 940,169), 2-mercapto-1,3,4-oxadiazoles or 1-phenyl-5-mercaptotetrazole (U.S. Pat. No. 3,173,789), DL6,8-dithiooctanoic acid (U.S. Pat. No. 3,318,701), 1-mercaptobenzoic acid (British Patent No. 1,144,481) aliphatic mercaptocarboxylic acids (U.S. Pat. No. 3,628,955), L-thiazolidine-4-carboxylic acid (J. Photogr. Sci., 13, 233 (1965)), divalent sulfur compounds (JP-A- No. 52-36029 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")), 2-mercaptobenzoxazole, 2-mercaptobenzimidazole (Photogr. Sci. Eng., 20, 220 (1976)), etc.
However, all of these compounds are still unsatisfactory as antisludging agents for use in photographic developers, particularly developers which contain a compound capable of dissolving silver halide, such as a highly concentrated sulfite. Many of the mercapto compounds rapidly lose their antisludging effect as a result of air oxidation or a reduction reaction between a disulfide compound produced by the oxidation and a sulfite ion. In the case when a large amount of silver salt is dissolved, sparingly soluble silver salts are formed to stain films, degree of which, however, depends upon the added amount. In some cases, they inhibit development when added in large amounts. Further, some compounds give an offensive smell. The above-described compounds also have such a low water solubility that it is difficult to add them in amounts necessary for preventing sludge formation.